Measurement Uncertainty (MU), Accuracy, Precision - Relationship?

P

pagnonig

#1
Hi All,

I'm a bit confused about how Measurement Uncertainty relates to Measurement Accuracy and Precision.:confused:

Could anybody help me (examples will be much appreciated!).

Thank you.
Giuseppe:thanx:
 
Elsmar Forum Sponsor
B

Benjamin28

#2
Accuracy is the closeness of a measured value to it's true value.

Precision is the repeatability of those measurements.

Uncertainty is a scientific quantification of the amount of error in a measurement when you take into account the many different variables which can effect it.

You can not truly know the accuracy of a measurement without knowing the Measurement uncertainty and you can not calculate the measurement uncertainty until you know the precision and much more.
 
P

pagnonig

#3
Accuracy is the closeness of a measured value to it's true value.

Precision is the repeatability of those measurements.

Uncertainty is a scientific quantification of the amount of error in a measurement when you take into account the many different variables which can effect it.

You can not truly know the accuracy of a measurement without knowing the Measurement uncertainty and you can not calculate the measurement uncertainty until you know the precision and much more.
Dear Benjamin,

thank you for the info.
Could you please suggest/post any document which explains, in simple terms, the concepts you summarized.

Giuseppe
 
U

Umang Vidyarthi

#4
Dear Benjamin,

thank you for the info.
Could you please suggest/post any document which explains, in simple terms, the concepts you summarized.

Giuseppe
Hello Pagnonig,

Benjamin has provided good answers here. I surmise from your post, that you perhaps are not well versed on the subject. I suggest you go through the MSA manual published by AIAG. Rummaging through the section E & F of chapter 1 will provide you with more clarity.

You may also benefit from the SPC newsletter, I am providing link for four very good articles :

http://www.spcforexcel.com/ezine/sept2007/sept_2007.htm

http://www.spcforexcel.com/ezine/oct2007/oct_2007.htm

http://www.spcforexcel.com/ezine/nov2007/nov_2007.htm

http://www.spcforexcel.com/ezine/dec2007/dec_2007.htm

Besides, you just google and find plenty of sites offering articles,books,and training. Here are some :

http://www.statgraphics.com/measurement_systems_analysis.htm

http://www.minitab.com.mx/training/TrainingSampleMeasurementSystems.pdf

http://www.qualitytrainingportal.com/resources/msa/index.htm

http://ezinearticles.com/?Measurement-System-Analysis-(MSA)&id=801704

Hope this helps

Umang :D
 
B

Benjamin28

#5
Giuseppe I don't really have such a document at hand myself. I would think that a physics teacher or a good beginner's book in metrology would be a good source for basic definitions and learning examples.

For examples of each concept I would use something along these lines.

Accuracy: Brad measures the outside diameter of a washer to be 0.20 inches, the true value of the OD is 0.20 inches and therefore his measurement is accurate. (so accuracy is described as a comparison of a measured value to it's true value)[it should be noted that the true value of a measurement can be infinitely small and therefore can never truly be known]

Precision: Brad uses a different instrument to measure the OD of the same washer and it reads 0.22" so he measures 10 more times and gets the same reading all ten times....it would be said that the instrument is very precise but not accurate.

Uncertainty: Brad uses his superior metrology skills to assess the uncertainty of measurements in his caliper as +/- 0.0005". In this way Brad can safely say that measurements made by this instrument utilizing a sound measurement method in a controlled setting will be within that interval 98% of the time.


These are pretty simplified examples, and as I said I'm sure you could find better ones from a physics teacher or a physics book but I hope this is of some help to you. ;)
 
P

pagnonig

#6
Giuseppe I don't really have such a document at hand myself. I would think that a physics teacher or a good beginner's book in metrology would be a good source for basic definitions and learning examples.

For examples of each concept I would use something along these lines.

Accuracy: Brad measures the outside diameter of a washer to be 0.20 inches, the true value of the OD is 0.20 inches and therefore his measurement is accurate. (so accuracy is described as a comparison of a measured value to it's true value)[it should be noted that the true value of a measurement can be infinitely small and therefore can never truly be known]

Precision: Brad uses a different instrument to measure the OD of the same washer and it reads 0.22" so he measures 10 more times and gets the same reading all ten times....it would be said that the instrument is very precise but not accurate.

Uncertainty: Brad uses his superior metrology skills to assess the uncertainty of measurements in his caliper as +/- 0.0005". In this way Brad can safely say that measurements made by this instrument utilizing a sound measurement method in a controlled setting will be within that interval 98% of the time.


These are pretty simplified examples, and as I said I'm sure you could find better ones from a physics teacher or a physics book but I hope this is of some help to you. ;)

Thank you very much to both of you for your valuable help!
Giuseppe
 
U

Umang Vidyarthi

#7
Thank you very much to both of you for your valuable help!
Giuseppe
You are welcome. :bigwave: There is more material on the cove. Click on the forum discussion thread index (located on left hand top in third row, highlighted in blue). In the index, click on 'Measurement Uncertainty (MU)', to open the pandora box.

There is another valuable thread you may benefit from- 'Accuracy vs Precision-what is more important for process capability'.

Here : http://elsmar.com/Forums/showthread.php?t=22349

Umang :D
 
Thread starter Similar threads Forum Replies Date
B IEC 60601-2-10 - Accuracy of Pulse Parameters - Required Measurement Uncertainty IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
W Dimensional Measurement of 10% accuracy and 25% uncertainty standard General Measurement Device and Calibration Topics 6
A Uncertainty Measurement - What this accuracy specification "1% + 10^5": means? General Measurement Device and Calibration Topics 2
P Measurement Uncertainty and Equipment Accuracy Measurement Uncertainty (MU) 2
N Is it normal if measurement uncertainty is less than equipment accuracy Measurement Uncertainty (MU) 2
T 4:1 Test Accuracy Ratio (TAR) or Stated Measurement Uncertainty (MU) General Measurement Device and Calibration Topics 21
A Measurement Uncertainty - Attenuation Accuracy Measurement Uncertainty (MU) 2
M Measurement Uncertainty in Optical Microscopy Measurement Uncertainty (MU) 1
G Does pitch/increment/resolution of a ruled scale apply to measurement uncertainty as line item? Measurement Uncertainty (MU) 10
R Uncertainty in measurement larger than tolerance Measurement Uncertainty (MU) 2
K ISO 17025:2017 clause 7.6.2 - Performing calibration of its own equipment shall evaluate the measurement uncertainty ISO 17025 related Discussions 6
G Reporting measurement uncertainty for custom items Measurement Uncertainty (MU) 2
K Measurement Uncertainty Budget (MU) of for Ultrasonic Thickness gauge Measurement Uncertainty (MU) 1
G Can Measurement Machine Bias be part of Uncertainty? General Measurement Device and Calibration Topics 1
D Difference between uncertainty and expanded uncertainty of measurement General Measurement Device and Calibration Topics 1
J Internal Laboratory Scope and Measurement Uncertainty (MU) IATF 16949 - Automotive Quality Systems Standard 1
C MU (Measurement Uncertainty) in an Internal Calibration Laboratory Measurement Uncertainty (MU) 1
B Measurement Uncertainty using Minitab Measurement Uncertainty (MU) 2
Marc Measurement Uncertainty Discussion Sub-Forum General Measurement Device and Calibration Topics 0
C Measurement Uncertainty fluctuates half a tick mark (20 millionths of an inch) Measurement Uncertainty (MU) 1
R MU (Measurement Uncertainty) of a Tensile Tester (e.g. Zwick Roell) Measurement Uncertainty (MU) 4
H Uncertainty Measurement Calculation in Chemical Testing Measurement Uncertainty (MU) 1
S MU (Measurement Uncertainty) for Oscilloscope Calibration Measurement Uncertainty (MU) 2
T Method Repeatability for MU (Measurement Uncertainty) Measurement Uncertainty (MU) 1
S Combined Uncertainty of an Indirect Measurement Measurement Uncertainty (MU) 8
N Uncertainty calculation for a voltage measurement Measurement Uncertainty (MU) 3
T Measurement of uncertainty for standard mechanical properties General Measurement Device and Calibration Topics 1
K New Gauges calibration certificate shows deviations from the measurement uncertainty IATF 16949 - Automotive Quality Systems Standard 5
A Calculating Combined Measurement Uncertainty - VDA 5 Measurement Uncertainty (MU) 1
T Uncertainty of Measurement vs. Tolerance Measurement Uncertainty (MU) 5
A Calibration Method and Measurement Uncertainty General Measurement Device and Calibration Topics 5
Geoff Cotton Measurement Uncertainty (MU) of HR-150A Rockwell Hardness Tester Measurement Uncertainty (MU) 1
Jerry Eldred When Does Resolution of Measurement Standard Apply in Uncertainty Calculations General Measurement Device and Calibration Topics 14
E Uncertainty Measurement for Water COD, TDS, TSS & pH Measurement Uncertainty (MU) 1
D General Procedure for Uncertainty Measurement Measurement Uncertainty (MU) 2
S Measurement Uncertainty for Neutral Salt Spray test to BS EN ISO 9227:2006 General Measurement Device and Calibration Topics 4
S Organizing Uncertainty Budgets for different Measurement Equipment Measurement Uncertainty (MU) 4
B Length Measure - Interpreting Calibration Results and Measurement Uncertainty (MU) Measurement Uncertainty (MU) 3
R Procedure for Measurement Uncertainty Estimation for Electrical Measurements Measurement Uncertainty (MU) 2
R Signal Conditioning Card - Calibration Measurement Uncertainty Measurement Uncertainty (MU) 5
K AATCC 81 pH test - How to calculate MU (Measurement Uncertainty) Measurement Uncertainty (MU) 2
optomist1 Definition Measurement Uncertainty - Standard definitions for Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 8
S Uncertainty Estimation in Temperature Measurement by K type Thermocouples Measurement Uncertainty (MU) 7
DietCokeofEvil ILAC-g8:03/2009 - Reporting Results with Measurement Uncertainty General Measurement Device and Calibration Topics 7
N Rounding the Numerical Value of the Measurement Uncertainty Measurement Uncertainty (MU) 2
A Uncertainty of Measurement for Calibration Laboratory? Measurement Uncertainty (MU) 8
C How to interpret Measurement Uncertainty (MU) Measurement Uncertainty (MU) 5
S ISO 19036 - Measurement Uncertainty for Microbiology Measurement Uncertainty (MU) 7
P Measurement Uncertainty Calculations Spreadsheet help General Measurement Device and Calibration Topics 4
L Measurement Uncertainty using Control Chart Measurement Uncertainty (MU) 2

Similar threads

Top Bottom